1. Technical Field
The present invention relates to printers that print predetermined characters or images by ejecting, for example, fine liquid ink drops of multiple colors from multiple nozzles to form fine particles thereof (ink dots) onto a print medium.
2. Related Art
Such printers can easily provide low-cost high-quality color prints. Accordingly, they have come into wide use not only among office users but also among ordinary users with the widespread use of personal computers and digital cameras.
Such printers print predetermined characters or images onto a print medium to produce desired prints by discharging (ejecting) liquid ink drops from the nozzles of their print head (also referred to as a liquid ejection head) to form fine ink dots onto the print medium while relatively moving the print medium and the liquid ejection head. Among them, printers that move a liquid ejection head placed on a moving body, called a carriage, in the direction intersecting the direction of transportation of print media are generally referred to as multipass printers. On the other hand, printers capable of so-called one-pass printing by a liquid ejection head that is long in the direction of transportation of print media (which may not be of an integral type) are generally referred to as line head printers.
Some of these printers perform printing by applying electrical charge to, for example, a transporting belt, transporting a substantially insulating print medium electrostatically adsorbed to the transporting belt, and ejecting ink drops from a liquid ejection head onto the print medium transported. Another printer transports a print medium adsorbed on a transporting belt by negative air pressure. Such print-medium transporting methods are useful particularly for line head printers. The printer described in JP-A-2005-75475 has: two line-head liquid ejection heads at the upstream and downstream portions of the transportation of print media; and two sets of transporting units corresponding to the liquid ejection heads in the direction of transportation of print media, the transporting units each having a plurality of transporting belts disposed at predetermined intervals in the direction intersecting the direction of transportation of print media. This printer performs printing by transporting a print medium that is electrostatically adsorbed on the transporting belts, and ejecting ink drops onto the transported print medium from the upstream and downstream liquid ejection heads. The liquid ejection heads are disposed between the transporting belts. The troubles of the nozzles of the liquid ejection heads are resolved using a cleaning unit disposed directly under the liquid ejection heads, in other words, the nozzles are cleaned.
With such printers in which transporting units each having a plurality of transporting belts are disposed in the direction of transportation of print media, as disclosed in JP-A-2005-75475, a print medium on the transporting belts of the transporting unit upstream in the direction of transportation of print media (hereinafter, simply referred to as an upstream transporting unit) is moved at one point or substantially at one point (linearly as viewed from the top of the print medium) to the transporting belts of the transporting unit downstream in the direction of transportation of print media (hereinafter, simply referred to as a downstream transporting unit) as viewed from the cross direction of the transporting belts. That is, the rear end of the print medium in the direction of transportation (hereinafter, simply referred to as the rear end of the print medium) is separated from the transporting belts of the upstream transporting unit at the same time or substantially at the same time. With the line head printers, for which high-speed printing is required, the rear end of the print medium is separated from the transporting belts of the upstream transporting unit in an instant. This instant separation of the rear end of the print medium from the transporting belts of the upstream transporting unit may cause vibrations to thereby distort images printed on the print medium transported by the downstream transporting unit, resulting in the possibility of a decrease in image quality.